The present invention relates to a method of injection of grout into soil comprising the steps of boring soil and injecting the grout, and repeating the above steps using a boring and grout injection rod having a packer at the lower portion thereof in which a grout injection tube may be used as a boring rod.
Various grout injection methods heretofore have been proposed. One of the most considerable difficulties has been in rotation and axial movement of boring rod. When instantaneously curable grout, the gellation time of which is several seconds to several minutes is used, a firmly solidified mass is formed around the injection tube. Accordingly, the injection rod is firmly anchored by the solidified mass therearound, occasionally resulting in difficulty of rotation and extraction of the rod. Although this difficulty may be solved by the use of a grout having a longer gellation time (several minutes to several ten of minutes), a solidified soil mass which is in cylindrical form with respect to the axis of rod can not be obtained. In particular, this is remarkable in complicated formation of soil. In order to position the injection tube in place, it is necessary to prevent the curvature of bore hole. It is occasionally impossible to avoid the curvature of bore hole since the injection tube generally bends under the influence of biasing force from the soil.
Various methods are adopted such as sealing, with hardened grout, an interstice between the bore wall and an injection tube or inflating a packer attached to the injection tube by feeding compressed air through a pipe during the injection to prevent the leakage of the grout to the ground surface. However, the former sealing method with a grout generally involves leakage of much grout or "jamming" due to high resistance of the grout seal. The latter method using a packer is not desirable when the bore hole wall is rough or working is accomplished at much greater depth. A new injection tube having a packer attached thereto should be inserted into bore hole after the boring has been completed. Such work requires alternative steps of boring and grouting which is time-consuming. There has been proposed a method of inserting a casing pipe into an injection area and then inflating the packer attached to an injection tube within the casing pipe when the bore wall is rough. However, the cost of a casing pipe and the work in its insertion is so high that such cost can not be neglected.